The invention relates generally to a process and arrangement for treating roasted coffee, especially roasted coffee beans.
More particularly, the invention relates to a process and arrangement for treating roasted coffee which, after treatment and grinding, is packaged in packets for ultimate use in coffee brewing machines.
Industrially roasted coffee should be well packed so as to maintain, for as long as possible, those properties which make brewed coffee palatable. It is well known that, soon after coffee is roasted, it begins to generate gas having a high percentage of carbon dioxide and that such gas evolution may continue for weeks. It is also known that, if the coffee is not properly treated and/or packaged, some of the coffee's aromatic volatile substances are lost with the gas. On the one hand, then, it is advisable to pack the coffee in sealed bags soon after roasting so as to prevent the loss of aromatic substances. On the other hand, the gas evolution makes it inadvisable to immediately package the freshly roasted coffee in sealed bags since the gas could produce too high a pressure in the bags.
In current processes for the treatment of coffee, the roasted coffee is allowed to liberate gas before being packaged. During this procedure, care must be taken to prevent escape of the aromatic substances from the coffee and to prevent oxidation of the aromatic substances by the oxygen in the air since this affects the quality of the aromatic substances. Thus, the roasted coffee is generally allowed to stand in airtight containers under controlled pressure with the liberated gas being removed by blowing inert gas into the containers. Such a procedure is described, for example, in the Canadian Patent No. 853,634. According to the Canadian patent, roasted coffee is permitted to liberate gas in airtight containers and the liberated gas is evacuated by blowing a purging gas into the containers in a controlled manner such that the pressure inside the containers is lower than atmospheric pressure but higher than the vapor pressure of at least the majority of the volatile constituents of the coffee. This procedure is relatively rapid. If the coffee is to be packaged in the form of beans, it is left in the containers for 4 or 5 days after which it is removed and packed in airtight packages under an inert gas atmosphere. On the other hand, if the coffee is ground before it is placed in the containers, the coffee is permitted to remain in the containers for only a few hours.
The foregoing procedure has the drawback that the brewed coffee does not have a fully satisfactory taste.